The present invention relates to a method for incineration for the disposal of a highly absorbent resin or a hydrophilic polymer electrolyte of a crosslinked structure, specifically an alkali metal salt thereof, and various absorbent articles comprising the above, with out the occurrence of any problem.
Absorbent articles, including disposable diaper, sanitary napkin or the like, comprise fluff pulp and highly absorbent resins as absorbent materials. Due to sanitary and hygienic concerns, conventionally, these absorbent articles have been incinerated and disposed after use, because these absorbent articles have been used to absorb urine or menstrual blood. However, although the fluff pulp dose not raise particular problems during incineration and disposal, the incineration and disposal of highly absorbent resins in the absorbent articles is potentially problematic as follows;
1. High ash content after incineration.
Ash content of fluff pulp incinerated at a high temperature, e.g., 800xc2x0 C. for 2 hours is about 0.1 wt %, while that of a highly absorbent acrylic resin is 40 to 60 wt %.
2. Alkaline ash.
Highly absorbent resins are generally in the forms of alkali metal salts of polymers, particularly sodium salts and potassium salts of polymers.
3. Highly absorbent resins are readily solidified into rubbery state after incineration.
4. During and after incineration, highly absorbent resins or the resulting ash readily attach to the incinerator wall or base, after which they are difficult to remove.
5. Highly absorbent resins damage the inside of the incinerator (because of the properties described above in 1 to 4).
These hidden problems have not been clearly recognized, so that currently, absorbent articles comprising highly absorbent resins are still mainly disposed of through incineration.
Nevertheless, the problems may well be addressed in near future because of the following reasons.
1. Because the thickness and weight of absorbent articles are being downsized of their and because the ratio of the cost of highly absorbent resins to the cost of pulp is being reduced, the ratio of highly absorbent resins is likely to increase in new absorbent articles while the ratio of fluff pulp therein is likely to decrease.
2. Due to the spread of disposable diaper usage among aged people, the ratio of absorbent articles or highly absorbent resins to the total amount of wastes to be incinerated is likely to increase.
3. Because the volume of wastes to be incinerated is likely to decrease due to the enforcement of the Container and Package Law Recycling, the ratio of the absorbent articles or highly absorbent resins to the total amount of wastes to be incinerated will likely increase.
4. Wastes from institutions for aged individuals and hospitals are often incinerated in these institutions"" own equipment. The ratio of the absorbent articles or highly absorbent resins to the wastes to be incinerated by this equipment is higher than the ratio thereof for general wastes.
To overcome these problems, no effective means has been established from the side of suppliers of highly absorbent resins and absorbent articles. At present, measures to improve the function of incinerators or to apply various maintenance strategies at incineration sites, have been relied upon.
In accordance with the invention, a means is provided for dealing directly with highly absorbent resins and absorbent articles, wherein among the problems involved in the incineration of these absorbent resins, the means can overcome the problem causing the incinerator damage due to the deposition inside the incinerator.
It is an object of the invention to provide a highly absorbent resin or an absorbent article comprising the highly absorbent resin, whereby the melting and solidification of the highly absorbent resin as well as the deposition thereof inside the incinerator can be prevented during the incineration thereof.
It is an additional object of the invention to provide a disposal bag or packaging material for a highly absorbent resin or an absorbent article comprising the highly absorbent resin, whereby the melting and solidification of the highly absorbent resin as well as the deposition thereof inside the incinerator can be prevented during the incineration thereof.
It is a still additional object of the invention to provide a method for incinerating a highly absorbent resin or an absorbent article comprising the highly absorbent resin, wherein the method can prevent the melting and solidification of the highly absorbent resin or can prevent the deposition thereof inside the incinerator during incineration.
The inventors have found that specific metal compounds are effective in overcoming the problems relating to the incineration of highly absorbent resins as described above. Thus, the invention has been achieved. More specifically, the incineration of a highly absorbent resin together with specific polyvalent metal compounds can reduce the problems. Therefore, absorbent articles comprising the highly absorbent resin can be incinerated well, with no need of any sophisticated incinerator or any increase of maintenance labor, at incineration sites. Detailed description will now follow.
1. A highly absorbent resin comprising a polyvalent metal compound capable of preventing the melting and solidification of the highly absorbent resin and the deposition thereof on the wall of an incinerator during the incineration of the highly absorbent resin.
2. An absorbent article comprising a highly absorbent resin and a polyvalent metal compound capable of preventing the melting and solidification of the highly absorbent resin and the deposition thereof on the wall of an incinerator during the incineration of the absorbent article.
3. A disposal bag for the disposal of a highly absorbent resin or an absorbent article comprising a highly absorbent resin or a packaging material for wrapping a highly absorbent resin or an absorbent article comprising a highly absorbent resin, the disposal bag or the packaging material comprising a polyvalent metal compound capable of preventing the melting and solidification of the highly absorbent resin and the deposition thereof on the wall of an incinerator during the incineration of the disposal bag or the packaging material and its contents.
4. A package comprising a highly absorbent resin or an absorbent article comprising a highly absorbent resin, and a packaging material housing the highly absorbent resin or the absorbent article, wherein a polyvalent metal compound or a solution thereof capable of preventing the melting and solidification of the highly absorbent resin and the deposition thereof on the wall of an incinerator during the incineration of the highly absorbent resin is packed in the packaging material along with the highly absorbent resin or the absorbent article.
5. A method for incinerating and disposing a highly absorbent resin or an absorbent article comprising a highly absorbent resin, comprising adding a polyvalent metal compound or a solution thereof to prevent the melting and solidification of the highly absorbent resin and the deposition thereof in an incinerator during incineration and disposal.